I. Field of the Invention
The present invention relates to dynamic ballast and stabilization systems for deep-sea applications, and, in particular, the present invention relates to a dynamic ballast and stabilization system for off-shore platform structures.
II. Description of the Prior Art
To be both practical and useful, off-shore platforms utilized for the exploration and production of crude oil and gas sources must not only perform a desired function but do so under adverse operating conditions. Primarily among such conditions is a virtually unpredictable source of trouble at any off-shore platform by the continuously changing pattern of wave intensity which reflects widespread weather conditions. For example, weather situations in one part of the world may have a decided effect on the water and wave conditions in a remote section thousands of miles away. In the design and construction of off-shore platforms most weather conditions can be accounted for through the expediency of fabricating the platform of sufficient strength to satisfactorily support the required constant and expected load and to overcome and to resist the most adverse storm conditions. Thus, a platform might be engineered to be sufficiently rugged by sheer massiveness to resist hurricane forces at the water surface without collapse or even to avoid excessive damage. The ideal situation would be to design the platforms to safely resist maximum forces as would be instituted by a hurricane or other severe storm. What is more difficullt to overcome, however, is the problem instituted by the pulsating forces resulting from periodic wave movement. While such movement may be particularly intense, the periodic forces generated by the waves may be of such frequency that, if counted over a period of time, will prompt and amplify an oscillatory movement of the floor-anchored platform structure. This vibrational tendency will be a function of the platform structure and the intensity and frequency of the wave forces.
While it is possible through engineering techniques to adequately design a platform to overcome the normal and expected wave forces, it is highly impractical in both structural and economical terms to design a platform when vibration and oscillation forces are taken into consideration. It can be readily appreciated that for platforms usable in deep waters the design problems are sharply aggravated as the platform height increases. For example, for extreme depths having an order of magnitude of 400 to 1,000 feet, it is virtually impossible to design and engineer a safe, practical platform. To overcome constantly imposed vibrations or oscillation inducing forces as well as the ordinary natural forces acting against an off-shore platform structure, many expedients have been resorted to such as internal bracing and external anchoring. In the absence of the latter, structures in relatively deep water often utilize an anchoring system including chains and cables both of which elements present troublesome handling problems and are not entirely effective. Furthermore, since the present trend in oil exploratory and production efforts is towards deeper waters, and anchoring systems tend to become more expensive and unwieldly, thereby amplifying the above-noted susceptibility to sway and vibrational tendencies.
An example of one solution of the aforementioned problem is disclosed in U.S. Pat. No. 3,553,968.